Rice bran oil has been touted to have a number of healthful benefits and uses. For example, House, U.S. Pat. No. 5,213,026, discloses the use of rice bran oil as a cooking oil. Hammond, U.S. Pat. No. 5,153,019, discloses a beverage product of rice bran and honey which is substantially free of spores, proteins, and coliform bacteria, and a whey protein concentrate. Taylor, U.S. Pat. No. 5,552,167, discloses a method for stabilizing high linolenic edible oils, such as soybean oil and canola oil, by blending the oils with rice bran oil in amounts effective to render the oils stable to oxidation. Imai, U.S. Pat. No. 5,514,398, discloses an additive for cholesterol-containing food that contains a rice bran component and/or derivative thereof as an active ingredient. Imai discloses that the rice bran oil component helps control blood cholesterol levels. Other studies disclose that a higher ratio of rice bran oil in a blended oil has a higher effectiveness for lowering cholesterol levels than the individual oils. Rice bran oil is also being promoted as an edible oil in China, Korean, Japan, and India. Studies done in these countries have shown a significant reduction in serum cholesterol and triglyceride levels within 15 to 30 days after including rice bran oil in one's diet. In Japan it has been reported that the effect can be seen within seven days.
Tocopherol and tocotrienols, collectively referred to as tocols, are monophenolic as well as lipophilic compounds and are present abundantly in rice bran oil as well as palm oil, soybean oil, sunflower oil and other oils. Tocols also occur widely in many plant tissues and other oil seeds.
Tocopherols are important biological anti-oxidants with vitamin E activity. Tocopherols that exhibit maximum vitamin E activity help prevent oxidation of lipids including polyunsaturated fatty acids. In addition, tocopherols are free radical scavengers and quench lipid free radicals. The antioxidant and free radical quenching properties coupled with the vitamin E activity of tocols make tocols useful in the treatment of various degenerative diseases such as aging, cancer, arthritis, damage to cells caused by air pollution and also in preventing coronary heart diseases.
It is well known that tocotrienols exhibit strong anti-oxidant activities or physiological activities. Pearce, U.S. Pat. No. 5,204,373, discloses that tocotrienols have been shown to inhibit cholesterol biosynthesis and cause a subsequent drop in LDL cholesterol, apolipo-protein B, thromboxane B2, platelet factor 4 and glucose levels. Kato, GB Pat. No. 2,117,381 A, discloses that tocotrienols have long been utilized as an antisterility drug for animals. Wright, U.S. Pat. No. 5,348,974, discloses the antioxidative activity of tocotrienols, which are known to play pivotal roles in the genesis of atherosclerotic plaques, thrombotic episodes, ischemic damage, cancer, aging, dementia, and inflammatory conditions. Physiological actions attributed to tocotrienols include decreasing serum cholesterol, decreasing hepatitic cholesterol synthesis and anti-tumor activity.
Gamma oryzanol (.gamma.-oryzanol) is another important biological anti-oxidant present in rice bran oil in significant quantities. Important effects resulting from .gamma.-oryzanol intake include decreasing plasma cholesterol, decreasing platelet aggregation, decreasing hepatitic cholesterol biosynthesis, increasing fecal bile acid excretion and decreasing cholesterol absorption. Gamma-oryzanol has also been used in treatments for nerve imbalance and menopause disorders.
Some definitions of terms which may be used throughout this patent:
Tocol--A mixture of one or more compounds selected from tocopherols (T), tocotrienols (T3), and tocotrienol-like (T3-like) compounds.
Tocotrienol-like compounds--Any biologically active compound that is contained in or derived from a biological source, and (1) which is released, or whose release is facilitated, upon stabilizing that source, or (2) whose recoverable amount in that source is increased by stabilizing that source. Such tocotrienol-like compounds include any biologically active compound displaying the biological activity of a tocotrienol which inhibits the activity of HMG-COA reductase as measured by an in-vitro HMG-COA reductase assay.
Tocotrienol-like compounds include, but are not limited to, any electron transfer ring compounds, anti-oxidant type compounds, redox compounds and compounds similar to or containing the three structural features that characterize the tocotrienols generally. Specific examples of T3-like compounds are ubiquinones, plastoquinones, isoquinones, phylloquinones, benzoquinones, flavanols, flavanoids, coumarins, unsaturated terpenoids and unsaturated isoprenoids. The term "T3-like compound" also encompasses analogues, homologs, isomers and derivatives of such compounds, such as prenylated derivatives or pyrolytic derivatives.
Gamma oryzanol (.gamma.-oryzanol)--any ferulic acid ester of triterpenyl alcohols. As used herein, .gamma.-oryzanol is any fraction containing ferulate esters of triterpene alcohols and plant sterols.
Common sterols include cholesterol, beta sitosterol, campesterol, cycloartenol, 24-methylene cycloartenol.
Enhanced--The state of a stabilized biological source, wherein the recoverable amount of the anti-oxidants, including tocols and .gamma.-oryzanol, are increased beyond that normally recoverable from the biological source prior to stabilization.
General methods of obtaining crude rice bran oil from rice bran are known. For example, a process for extracting rice bran oil from rice bran is disclosed in Gastrock, U.S. Pat. No. 2,727,914. The process disclosed in Gastrock involves mildly cooking the rice, crisping the cooked particles, and then mixing with a solvent, such as hexane, and subjecting the resulting slurry to filtration. Imai, U.S. Pat. No. 5,514,398, discloses the following conventional method for extracting the components of rice bran: extracting oily components from rice bran with a solvent such as hexane, degumming, dewaxing and alkali refining these oily components, subjecting the oil to solid/liquid separation and distilling the residue, followed by a solvent-extraction and column treatment.
Mamuro, British Pat. No. GB 2 090 836 A, discloses a method for the preparation of a tocotrienol concentrate from oleaginous material, such as rice bran oil, comprising the following steps:
(a) dissolving or extracting an oleaginous material containing tocotrienols in or with a nonpolar organic solvent such as hexane to form a tocotrienol-containing solution; PA1 (b) contacting the tocotrienol-containing solution with an anion-exchange resin whereby the tocotrienols are absorbed on the anion-exchange resin; and PA1 (c) eluting the tocotrienols with an eluant out of the anion-exchange resin to give an eluate solution containing the tocotrienols.
More recently, Lane, U.S. Pat. No. 5,591,772, disclosed two separate protocols for extracting rice bran oil from stabilized rice bran using hexane and steam. Additionally, Lane discloses techniques for enhancing the yield of tocotrienol compounds by dissolving a tocotrienol rich fraction in hexane, and then binding the dissolved tocotrienol rich fraction to an amino column (1 ml) and then selectively eluting compounds using a solvent that does not elute impurities. However, this process is limited to selectively eluting a few tocotrienols and does not enhance the overall tocol content of rice bran oil.
Given the benefits of anti-oxidant products and the potential uses for rice bran oils, there is a need for a rice bran oil that is enriched with anti-oxidant products, including .gamma.-oryzanol and tocol products, so that the benefits of rice bran oil are better realized.